1. Field of the Invention
Methods and apparatuses consistent with the present invention relate to sharing a bus key.
2. Description of the Related Art
Recently, music and moving pictures contents are copied indiscreetly, and copied contents can be obtained easily. In order to prevent these problems from occurring, a digital rights management (DRM) method, that is, a method of protecting contents is recently highlighted and usage of the DRM method increases.
The DRM method of protecting contents is broadly classified into encryption and usage rights. That is, the DRM method prevents an unauthorized person from accessing contents by encrypting the contents, and also enables contents to be utilized only within an authorized scope, by checking the usage rights.
Despite the aforementioned methods, a third party can decipher a content encryption or eliminate a content period restriction which limits a content to be used only for a predetermined period, and then distribute the content so that anyone can utilize the content.
Accordingly, to prevent these problems from occurring, the DRM method provides a Robustness Rule that is the terms required for contents management devices to satisfy.
The DRM methods which are frequently used are Digital Transmission Content Protection (DTCP), Window Media Digital Right Management (WNDRM), and Advanced Access Content System (AACS). The Robustness Rule of these DRM methods generally requires safe protection of an encryption key, protection of deciphered contents against being disclosed to the exterior of devices, and protection of deciphered contents against being disclosed to user accessible buses within devices, for example, a peripheral component interconnect (PCI) bus, an integrated drive electronics (IDE) bus, or a universal serial bus (USB).
In particular, in order to manufacture a device which satisfies the term requiring the protection of the deciphered contents against being disclosed to user accessible buses, a related art method is encrypting data with a predetermined bus key before the data is transmitted through a bus.
Here, the bus key is generated by using a unique device key which is allocated to each device. However, in the related art method, the device key can be leaked to a third party thereby enabling the third party to generate a bus key. Also, when a bus key is leaked, a third party can decrypt data encrypted with the bus key, by using the bus key.